Failure of observation and impedance respirography to detect active expiration in ventilated preterm infants.

Twenty preterm infants ventilated for the respiratory distress syndrome were studied on 44 occasions to identify the pattern of interaction between their spontaneous respiratory efforts and the ventilator, using three techniques: (1) an oesophageal balloon and pneumotachograph, (2) impedance respirography and (3) clinical scoring. The information was in agreement on 23 of the occasions. In 7 infants the balloon and pneumotachograph showed active expiration which was not detected by the other methods. Four of these infants sustained a pneumothorax, one after paralysis with pancuronium. This study shows that only a system incorporating an accurate assessment of the baby's own respiratory pattern is able to detect different patterns of interaction. Impedance respirography and clinical observation appear to be unsatisfactory in this context.